The invention relates to an antiserum which reacts specifically with the early fibrin and fibrinogen degradation products (FDP) formed by the action of plasmin on fibrin and fibrinogen, referred to in the literature as "fibrinogen X (fg-X)" and "fibrinogen Y (fg-Y)", and it relates also to the preparation thereof.
The action of plasmin on fibrinogen produces fibrinogen degradation products which have acquired an increasing importance in the diagnosis and treatment of acquired hemorrhagic diatheses. Their detection can serve as a valuable diagnostic indication in a number of diseases. The most important diseases in which fibrinogen degradation products occur are listed summarily herewith:
1. Thrombotic diseases, such as venous thrombi, pulmonary embolism, myocardial infarction, coronary thrombosis; PA1 2. Bacterial infections; PA1 3. Carcinoma; PA1 4. Kidney and liver diseases; PA1 5. Obstetric complications.
The methods used heretofore for the recognition of FSP have been compared with one another in recent literature: MARDER, V. J., MATCHETT, M. O., SHERRY, S.: "Detection of serum fibrinogen and fibrin degradation products" Am. J. Med. 51: 71-82 (1971), THOMAS, D. P., NIEWIAROWSKI, S., MYERS, A. R. et al.: "A comparative study of four methods for detecting fibrinogen degradation products in patients with various diseases." N. Engl. J. Med. 283: 663-668 (1970), CARVALHO, A. C. A., ELLMAN, L. L., COLMAN, R. W.: "A comparison of the staphylococcal clumping test and an agglutination test for detection of fibrinogen degradation products." Am. J. Clin. Pathol. 62: 107-112 (1974).
All these methods have so many disadvantages that they have never been adopted into clinical routine testing.
In the proteolysis of fibrinogen with plasmin, the first recognizable degradation product is fg-X. It has a molecular weight of approximately 270,000. Fg-X can be brought to coagulation by thrombin, differing in this regard from all other degradation products formed from fibrinogen. As the degradation of fibrinogen by plasmin continues a fragment fg-Y and a fragment fg-D are formed from fg-X. Fg-Y has a molecular weight of 190,000, and is itself further broken down to an fg-D and an fg-E (MARDER, F. J.: "Immunologic structure of fibrinogen and its plasmin degradation products. Theoretical and clinical considerations." In Fibrinogen, ed. Laki, K., 1969, Marcel Dekker, Inc., New York, and Edward Arnold (Publishers, Ltd.), London, 339-358. PIZZO, S. V., SCHWARTZ, H. L., HILL, R. L., and McKEE, P. A.: "The effect of plasmin on the submit structure of human fibrin." J. Biol. Chem. 248: 4574-4583 (1973).
The fragments fg-D and fg-E are referred to as plasmin-resistant fragments of fibrinogen (BUDZYNSKI, A. Z., STAHL, M., KOPEC, M., LATALLO, Z., KOWALSKI, E.: "High molecular weight products of the late stage of fibrinogen proteolysis by plasmin and their structural relation to the fibrinogen molecule." Biochem. Biophys. Acta, 147: 313-323 (1967)). They comprise about 70% of the original fibrinogen molecule. The degradation products of fibrin (fb) resemble those of fibrinogen, except that fibrin-X (fb-X) is not coagulable by thrombin since it lacks the A and B peptides which are still present in fg-X. Also, the fibrinogen degradation products form soluble complex compounds with still-undegraded fibrinogen, as they do with fibrin monomers. The molecular weights of the complex compounds thus formed extend from 400,000 to 1,000,000.
The most important biological action of the fibrinogen degradation products is based on their antithrombin activity (such products are also referred to as "antithrombin IV"). The antithrombin activity of the early degradation products (fg-X and fg-Y) is about 10 times greater than that of the late degradation products (fg-D and fg-E). Electron microscope studies (BANG, N. V., FLETCHER, A. P., ALKJAERSIG, N. AND SHERRY, S.: "Pathogenesis of the Coagulation Defect Developing During Pathological Plasma Proteolytic (Fibrinolytic) Sates. III--Demonstration of Abnormal Clot Structure by Electron Microscopy." J. Clin. Invest. 41: 935-943 (1962) Part I) have shown that fibrin formed in the presence of fibrinogen degradation products differs greatly from normal fibrin, probably as a result of an abnormal polymerization.
The fibrin and fibrinogen degradation products are usually determined by immunological methods in which a fibrinogen antiserum is used. These methods are unsuitable for the determination of such degradation products, since the fibrinogen contained in the plasma also reacts with the fibrinogen antiserum. Since the early FDP's, such as fg-X and the larger complex compounds can be coagulated with thrombin and therefore are removed from the plasma in the coagulation procedure, the serum does not contain the entire spectrum of the fibrin and fibrinogen degradation products. Only the fragments Y, D and E and the smaller peptides are present in the serum, but not fragment X.
Antiserums against fg-D and fg-E are known. They show no cross reaction against antifibrinogen or with one another. They are used for distinguishing different fibrin and fibrinogen degradation products. Hitherto it has not been possible to prepare antiserums against fg-X and fb-X or against fg-Y and fb-Y, namely the early degradation products of fibrinogen. On account of the pronounced antithrombin action of these fibrin and fibrinogen degradation products, it would be desirable to have antiserums against these products, too, so as to be able to detect them directly in the plasma.